Abstract
The method of sulfuric acid analysis is well established. At present, the concentration of sulfuric acid can be analyzed automatically on actual production lines by using neutralization titration method. With the case of a mixed solution of nitric and hydrofluoric acid, however, measuring each acid content and the concentration of iron contained therein with speed and accuracy suitable for actual operation is very difficult even using the presently available acid separation techniques. A primary reason for this is that no piece of equipment with that level of measuring capability has not been developed yet.
In the preliminary studies, the followings are verified:
(1) As a method of analyzing hydrofluoric acid, the iron-acetylacetone complex discoloration absorbance method is adopted.
(2) As a method of analyzing nitric acid, the method of subtracting the concentration of hydrofluoric acid from the total acid amounts obtained by neutralization titration is adopted.
(3) As a method of analyzing the iron content, the iron-salicylic acid complex absorbance method is adopted.
By fully automating the series of analytical processes described above, the following are achieved:
(1) The several hours needed to complete the analysis work can be shortened to about 40 min. Moreover, acid can be controlled with care and attention to detail, which will greatly contribute to the improvement of the quality of pickled coils.
(2) The work load of line operators can be reduced, making substantial labor saving possible.
